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depths in Antarctica and Greenland, and providing information 

 about the continental structure of Antarctica. Explorations in South 

 America showed the crust of the Andean massif to be unexpectedly 

 thin. Ground waves of ultralong period were subjected to intensive 

 study, demonstrating the value of such waves in detecting distant 

 earthquakes and underground explosions. 



SOLAR ACTIVITY 



IGY studies resulted in unprecedented observations of solar 

 activity, including an almost complete record of hydrogen gas flares. 

 Observations were enhanced by occurrence of the greatest number of 

 sunspots since 1612, when such phenomena were first observed by 

 Galileo. Solar clouds were shown to be the source of ultraviolet light, 

 solar flares the source of gamma radiation, and the corona the source 

 of X-rays. 82 Magnetic fields of varying intensities were found to 

 accompany sunspots and flares, with residual magnetic fields extend- 

 ing outward possibly beyond the solar system. Possibilities were 

 raised that much thermal energy might be transferred to the earth's 

 atmosphere by way of direct contact with the thin but hot gases of 

 the sun's corona. 



UPPER ATMOSPHERE 



IGY research established that there is no definite end to the 

 earth's atmosphere. As far distant as 10 earth diameters a sub- 

 stantial hydrogen atmosphere was found to exist, fading into the 

 atmosphere of outer space itself, dominated by the effects of untold 

 meteors, X-rays, ultraviolet light, protons, electrons, cosmic rays, 

 and electric and magnetic fields. Thus, the upper atmosphere was 

 found to be a place of considerable activity, affecting many phenomena 

 on the earth itself. Of tremendous interest was the discovery of the 

 two Van Allen radiation belts, • existing as annular shrouds about 

 the earth, shaped by terrestrial magnetic fields. These belts of intense 

 radiation were seen as important factors in determining and per- 

 haps limiting man's future exploration of space. 



Appraisal of Findings 



. If one particular field of activity were to be singled out as the most 

 outstanding scientific achievement of the IGY, it would undoubtedly 

 be the launching of artificial earth satellites. Although the IGY was 

 primarily an exercise in pure science, one of its primary objectives 

 was to exploit contemporary technology in the pursuit of scientific 

 objectives. The launching of the IGY artificial earth satellites repre- 

 sented a remarkable technological achievement that, despite advance 

 warning, nonetheless created astonishment and a sense of wonder 

 throughout the world. Thus, these scientific space probes clearly 

 initiated the space age, opening a new era of exploration and dis- 

 covery which nas progressed much more rapidly than could possibly 

 have been foreseen during the IGY. Sullivan has likened the scientific 



* X-rays are emitted when a beam of high-velocity electrons impinges upon a suitable metallic target 

 within an evacuated, or partially evacuated, glass tube. Powerful natural emitters of X-rays outside the 

 solar system are believed to Include radio sources, and novae and supernovae. Gamma rays, similar in 

 many respects to X-rays but generally of higher frequency and greater penetrating power, are emitted upon 

 the decay of radioactive substances. 



